1. Field of the Invention
The present invention relates to a dynamic pressure bearing apparatus installed in a motor.
2. Description of the Related Art
Ball bearings have been adopted as bearings in a variety of fans, such as axial fans and centrifugal fans. For example, ball bearings are adopted in a fan described in JP-A 2011-78224. Meanwhile, an oil-impregnated bearing obtained by sintering powder of a copper-based material is adopted in a fan described in JP-A 2000-14080.
A dynamic pressure bearing apparatus for use in a spindle motor of a disk drive apparatus is disclosed in JP-A 2005-321089. The dynamic pressure bearing apparatus includes a housing, a bearing sleeve, a shaft member, and a ring-shaped seal member. The bearing sleeve is fixed to the housing. The shaft member is arranged inside the bearing sleeve. The seal member is fixed to the shaft member on an upper side of the bearing sleeve. In the dynamic pressure bearing apparatus, a radial bearing portion is defined between an inner circumferential surface of the bearing sleeve and an outer circumferential surface of the shaft member. The shaft member is supported in a radial direction in a non-contact manner through the radial bearing portion. A first thrust bearing portion is defined between an upper end surface of the bearing sleeve and a lower end surface of the seal member. A second thrust bearing portion is defined between a lower end surface of the bearing sleeve and a flange portion provided at a lower end of the shaft member. The seal member and the flange portion are supported in a thrust direction in a non-contact manner through the first and second thrust bearing portions, respectively. A seal space is defined between an outer circumferential surface of the seal member and an inner circumferential surface of an upper end portion of the housing. A surface of a lubricating oil is kept always within a range of the seal space.
A spindle motor of a hard disk drive disclosed in JP-A 2000-175405 includes a hub having a rotor magnet attached thereto, and a base having stator coils attached thereto through a sleeve. An outer edge portion of the hub is arranged in proximity to the base, so that a labyrinth is defined between the hub and the base. Oil mist and the like generated in the spindle motor are thereby prevented from being dispersed, enabling the hard disk drive to achieve a high performance. A spindle motor disclosed in JP-A 2004-248481 includes a hub including a cylindrical projecting portion arranged to project downward. A labyrinth seal is defined by a combination of a clearance space between an upper surface of a bearing sleeve and a lower surface of a portion of the hub which is arranged radially inward of the projecting portion, a clearance space between an inner circumferential surface of the projecting portion and an outer circumferential surface of the bearing sleeve, and a clearance space between a lower surface of the projecting portion and a flange arranged around the bearing sleeve.